Method of in-situ cleaning for LPCVD teos pump

ABSTRACT

In one embodiment, the present invention relates to a method of cleaning a low pressure chemical vapor deposition apparatus having TEOS material build-up therein involving contacting the low pressure chemical vapor deposition apparatus with a composition containing at least one lower alcohol. In another embodiment, the present invention relates to a system for cleaning a low pressure chemical vapor deposition apparatus having TEOS material build-up therein, containing a supply of a composition comprising at least one lower alcohol; an injection port for introducing the composition comprising at least one lower alcohol into the low pressure chemical vapor deposition apparatus; and a pump/vacuum system for removing crystallized TEOS material build-up from the low pressure chemical vapor deposition apparatus.

TECHNICAL FIELD

The present invention generally relates to improved LPCVD processing. Inparticular, the present invention relates to reducing unwanted build-upin LPCVD pump systems thereby permitting temporary process stops withoutthe potential for lock-up and substantially increasing the timeintervals between servicing an LPCVD pump system.

BACKGROUND ART

Chemical vapor deposition (CVD) involves the formation of a solid filmon a substrate by the reaction of vapor phase chemicals that contain therequired constituents. The reactant gases are introduced into a reactantchamber and are decomposed and reacted at a heated surface to form thefilm. CVD techniques are widely employed in the fabrication ofsemiconductor structures; therefore, CVD techniques are some of thefundamental building blocks in semiconductor processing. Low pressurechemical vapor deposition (LPCVD) techniques involve, as the nameimplies, low pressures and are advantageous in that films having highpurity, excellent uniformity, and conformal step coverage areobtainable. LPCVD techniques are disadvantageous in that hightemperatures are typically required.

Another disadvantage associated with LPCVD processes involves theformation of tetraethylorthosilicate (TEOS) or Si(OC₂H₅)₄ films (orsilicon dioxide layers made from TEOS starting material). During theLPCVD TEOS film formation process, the starting gas is continuouslyintroduced into the reactor vessel, but a vacuum is continuously drawnfrom the reactor vessel through a vacuum extraction system connected tothereto, so that a predetermined low pressure is maintained in thereactor vessel to properly control the growth of the TEOS film. In manyinstances, the starting gas is not completely used in the formation ofthe TEOS film, and a large part thereof is undesirably pulled from thereactor vessel into the vacuum extraction system. As a result, thepump/vacuum system responsible for the low pressures, such as amechanical booster pump, a rotary pump, a blower, and other related pumpsystem elements, are damaged by the deposition therein of the startinggas pulled from the reactor vessel. In particular, the starting gaspulled from the reactor vessel is undesirably deposited in the pumpsthereby creating an unwanted build-up in an interior of the vacuumextraction system. TEOS byproducts also create an unwanted build-up inan interior of the vacuum extraction system. TEOS material build-up ischaracterized by a very sticky film. This is problematic because thebuild-up on internal surfaces of the LPCVD apparatus and particularly oninternal movable parts of the pumps requires frequent vigorouscleanings.

Moreover, TEOS is particularly problematic in LPCVD processes becauseTEOS gas condenses in the vicinity of 35° C. Problems ensue when anLPCVD TEOS film formation process is temporarily stopped, such as duringevening hours or during a power glitch causing the pump to shut off. Inparticular, after the LPCVD apparatus is turned off, the apparatus coolsdown to room temperatures from its high operating temperatures. SinceTEOS gas condenses around 35° C., TEOS materials build-up on variouselements of the LPCVD apparatus including the pump/vacuum system as thetemperature of the LPCVD apparatus cools down. Upon turning the LPCVDapparatus back on, blower vains, rotors and other elements of thepump/vacuum system cannot function properly due to the solid build-up ofTEOS material. In many instances, within only 30 minutes after stoppingand LPCVD TEOS film formation process, TEOS material builds-up soextensively that it is impossible to turn the LPCVD apparatus back on.Although it is sometimes desirable to temporarily interrupt the LPCVDTEOS film formation process in order to make minor process adjustments,such interruptions are avoided due to the possibility that the LPCVDapparatus cannot be turned back on.

Cleaning a pump/vacuum system in an LPCVD TEOS film formation processrequires one to disconnect the pump/vacuum system from the LPCVDapparatus, disassemble the pump/vacuum system, clean the individualparts, reassemble the pump/vacuum system, connect the pump/vacuum systemback to the LPCVD apparatus, and testing the cleaned system. Thiscleaning process typically takes three to four days, which is a longperiod of time to be off-line. Not only is this cleaning processcumbersome, but the LPCVD apparatus is rendered useless during the longcleaning time, thus inhibiting further semiconductor processing.

SUMMARY OF THE INVENTION

The present invention provides an improved LPCVD process by enabling thein situ cleaning of the pump/vacuum system of the LPCVD apparatus. Thecleaning is in situ in that the LPCVD apparatus is cleaned withouthaving to disconnect and disassemble the pump/vacuum system whilerunning. The present invention also provides methods for minimizing theaccumulation of TEOS material in the pump/vacuum system of the LPCVDapparatus. As a result of the present invention, LPCVD processing iscapabilities are lengthened, temporary stops in LPCVD processing arefacilitated, and cumbersome cleaning of the pump/vacuum system of theLPCVD apparatus is minimized and/or eliminated.

In one embodiment, the present invention relates to a method of cleaningan LPCVD apparatus having TEOS material build-up therein involvingcontacting the LPCVD apparatus with a composition containing at leastone lower alcohol.

In another embodiment, the present invention relates to a method ofreducing TEOS material build-up from interior surfaces of a pump/vacuumsystem of an LPCVD apparatus having a first amount of TEOS materialbuild-up involving contacting the pump/vacuum system of the LPCVDapparatus with a composition containing at least one lower alcohol undera pressure from about 0.001 Torr to about 800 Torr to provide thepump/vacuum system of the LPCVD apparatus having a second amount of TEOSmaterial build-up, wherein the second amount of TEOS material build-upis at least about 75% by weight less than the first amount of TEOSmaterial build-up.

In yet another embodiment, the present invention relates to an LPCVDmethod involving the steps of depositing TEOS on a first semiconductorsubstrate in an LPCVD apparatus; removing the first semiconductorsubstrate from the LPCVD apparatus; injecting a composition containingat least one lower alcohol into the LPCVD apparatus; and depositing TEOSon a second semiconductor substrate in the LPCVD apparatus.

In still yet another embodiment, the present invention relates to asystem for cleaning a low pressure chemical vapor deposition apparatushaving TEOS material build-up therein, containing a supply of acomposition comprising at least one lower alcohol; an injection port forintroducing the composition comprising at least one lower alcohol intothe low pressure chemical vapor deposition apparatus; and a pump/vacuumsystem for removing crystallized TEOS material build-up from the lowpressure chemical vapor deposition apparatus.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A, 1B and 1C are schematic representations of systems forcleaning a low pressure chemical vapor deposition apparatus having TEOSmaterial build-up therein according to three aspects, respectively, ofthe present invention.

DISCLOSURE OF INVENTION

The present invention involves improving LPCVD TEOS processing byreducing unwanted TEOS material build-up in a LPCVD apparatus using alower alcohol. Unwanted TEOS material build-up includes TEOS that isformed on the interior surfaces of the LPCVD apparatus, and particularlyon the interior surfaces of the pump/vacuum system of the LPCVDapparatus, as well as TEOS starting materials and byproducts formed onthese interior surfaces during the formation of a TEOS layer. Thestarting materials when forming a TEOS layer include TEOS and inertgases. LPCVD TEOS processing also includes the formation of a silicondioxide layer where TEOS is employed as a starting material therefor.

The present invention involves any CVD apparatus that employs lowpressures. Low pressures are pressures below about 10 Torr. In anotherembodiment, low pressures are pressures below about 1 Torr. Typically,CVD apparatuses that employ low pressures are LPCVD apparatuses, but CVDapparatuses that employ low pressures further include plasma enhancedchemical vapor deposition (PECVD) apparatuses that employ pressuresbelow about 10 Torr. For convenience, these apparatuses are collectivelyreferred to as LPCVD apparatuses. LPCVD apparatuses are known in theart, and are commercially available. There is no limitation with regardto the type of LPCVD apparatus employed.

The LPCVD apparatus is equipped with a pump/vacuum system thatestablishes and maintains the low pressure conditions within areaction/deposition chamber where a substance is formed on a substrate(such as a TEOS layer over a wafer substrate). Pump systems, vacuumsystems, extraction systems and the like for CVD apparatuses are knownin the art, and are commercially available. There is no limitation withregard to the type of pump/vacuum system employed.

One or more lower alcohols are contacted with the LPCVD apparatus and inparticular with the pump/vacuum system of the LPCVD apparatus in anysuitable manner. While not wishing to be bound by any theory, it isbelieved that the lower alcohol crystallizes the sticky TEOS materialbuild-up and the crystallized build-up vaporizes, which is then removedfrom the LPCVD apparatus through the pump/vacuum system. The amount oflower alcohol is primarily dependent upon the amount of TEOS materialbuild-up on/in the LPCVD apparatus and in particular on/in thepump/vacuum system of the LPCVD apparatus. Prior to contact with thelower alcohol composition, semiconductor substrates for receiving CVDmaterials are removed from the LPCVD apparatus.

Lower alcohols are alcohols containing from 1 to about 6 carbon atoms.In another embodiment, lower alcohols contain from about 2 to about 4carbon atoms. Lower alcohols may be represented by the formulaR(OH)_(x), wherein R is an organic group containing from 1 to about 6carbon atoms, such as an alkyl group containing from 1 to about 6 carbonatoms, and x is an integer from 1 to about 3. Examples of lower alcoholsinclude methanol, ethanol, n-propanol, isopropanol, n-butanol,isobutanol, t-butyl alcohol, pentanol, t-pentyl alcohol, neopentanol,hexanol, cyclohexanol, 3-methyl-2-pentanol, and mixtures of two or morethereof.

A composition containing the lower alcohol is contacted with the TEOSmaterial build-up. In one embodiment, the lower alcohol compositioncontacted with the TEOS material build-up is in the form of a liquid. Inanother embodiment, the lower alcohol composition contacted with theTEOS material build-up is in the form of a gas. In yet anotherembodiment, the lower alcohol composition contacted with the TEOSmaterial build-up is in the form of a mixture of a plasma and a gas.

One or more lower alcohols are contacted with the TEOS material build-upfor a time sufficient for the lower alcohol to reduce, minimize and/oreliminate TEOS material build-up on the interior surfaces of the LPCVDapparatus, and particularly on/in the pump/vacuum system of the LPCVDapparatus. In one embodiment, the time of which the lower alcoholcomposition is contacted with the TEOS material build-up is typicallyfrom about 1 second to about 1 hour. In another embodiment, the loweralcohol composition is contacted with the TEOS material build-up for aperiod of time from about 5 seconds to about 10 minutes. In yet anotherembodiment, the lower alcohol composition is contacted with the TEOSmaterial build-up for a period of time from about 10 seconds to about 60seconds.

In one embodiment, the liquid/gas composition containing one or morelower alcohols further contains water, a lower organic compound (anorganic compound containing 1 to about 6 carbon atoms) at least oneinert gas, such as nitrogen, and the noble gases. Lower organiccompounds include acetone, methylethyl ketone, methylisobutyl ketone,ethyl acetate, and the like. Noble gases include argon, helium, neon,krypton, and xenon. Water is tap water or deionized water, but deionizedwater is preferred.

In one embodiment, the liquid/gas composition contains from about 1% toabout 100% by weight of at least one lower alcohol, from about 0% toabout 99% by weight of water, from about 0% to about 99% by weight of atleast one lower organic compound, and from about 0% to about 99% byweight of at least one inert gas. In another embodiment, the liquid/gascomposition contains from about 2% to about 75% by weight of at leastone lower alcohol, optionally from about 10% to about 98% by weight ofwater, optionally from about 1% to about 25% by weight of at least onelower organic compound, and optionally from about 1% to about 98% byweight of at least one inert gas. In yet another embodiment, theliquid/gas composition contains from about 3% to about 50% by weight ofat least one lower alcohol, optionally from about 25% to about 97% byweight of water, optionally from about 2% to about 10% by weight of atleast one lower organic compound, and optionally from about 5% to about97% by weight of at least one inert gas.

Examples of such compositions include a gas containing about 50% byweight of at least one lower alcohol and about 50% by weight ofdeionized water vapor; a liquid containing about 50% by weight of atleast one lower alcohol, such as a pentanol, and about 50% by weight ofdeionized water; a liquid containing about 20% by weight of at least onelower alcohol, such as a butanol, about 70% by weight of deionizedwater, and about 10% by weight of a lower organic compound, such asacetone; a liquid containing about 10% by weight of at least one loweralcohol, such as a isopropanol, and about 90% by weight of deionizedwater; and a liquid containing about 10% by weight of at least one loweralcohol, such as ethanol, about 85% by weight of deionized water, andabout 5% by weight of a lower organic compound, such as acetone.

Any suitable pressure may be employed when using the lower alcoholliquid or gas composition. In one embodiment, the pressure in the LPCVDapparatus is from about 0.001 Torr to about 800 Torr. In anotherembodiment, the pressure in the LPCVD apparatus is from about 0.005 Torrto about 500 Torr. In one embodiment, the pressure in the LPCVDapparatus is from about 0.01 Torr to about 100 Torr.

The temperature during contact between the lower alcohol composition andthe TEOS material build-up is typically from about 10° C. to about 200°C. In one embodiment, the temperature during contact between the loweralcohol composition and the TEOS material build-up is from about 20° C.to about 150° C. In another embodiment, the temperature during contactbetween lower alcohol composition and the TEOS material build-up is fromabout 30° C. to about 100° C. The temperature is maintained to maximizethe reduction of the TEOS material build-up on the LPCVD apparatus,while not substantially damaging or degrading any of the apparatussurfaces.

Comparing the interior surfaces of the LPCVD apparatus (and particularlythe interior surfaces of the pump/vacuum system of the LPCVD apparatus)before and after contact with the lower alcohol composition, theinterior surfaces after contact have at least about 75% less TEOSmaterial build-up (for example, by weight) than the interior surfacebefore contact. In another embodiment, the interior surfaces aftercontact have at least about 90% less TEOS material build-up than theinterior surface before contact. In yet another embodiment, the interiorsurfaces after contact have at least about 98% less TEOS materialbuild-up than the interior surface before contact. In still yet anotherembodiment, the interior surfaces after contact have no visuallydetectable TEOS material build-up (by the naked eye).

Once the sticky/tacky TEOS material build-up is crystallized, it can beremoved from the LPCVD apparatus via the pump/vacuum system, such as bysublimation. The interior surfaces of the LPCVD apparatus andparticularly the pump/vacuum system are substantially free of thesticky/tacky TEOS material build-up after treatment with a lower alcoholcomposition, just as if the pump/vacuum system was disassembled andcleaned in a conventional manner.

Conventional LPCVD TEOS film formation processes require pump/vacuumsystem disconnection and disassembly for cleaning about every 3 months.When employing the processes of the present invention in connection withLPCVD TEOS film formation processes, pump/vacuum system disconnectionand disassembly for cleaning is required about every 12 months, if atall.

FIGS. 1A to 1C are schematic representations of systems for cleaning alow pressure chemical vapor deposition apparatus having TEOS materialbuild-up therein. FIG. 1A specifically shows an LPCVD system thatcontains at least a pump system having an inlet or injection port forthe lower alcohol composition and an outlet or exhaust through which thecrystallized TEOS material build-up is removed. FIG. 1B specificallyshows an LPCVD system that includes a pump system connected to an LPCVDchamber, the LPCVD chamber having an inlet or injection port for thelower alcohol composition wherein the crystallized TEOS materialbuild-up is removed through the outlet or exhaust. FIG. 1C specificallyshows a pump system, that may be contained within or connected to anLPCVD apparatus, containing an inlet typically connected to the LPCVDchamber, and an outlet or exhaust for removing the crystallized TEOSmaterial build-up.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described components (assemblies, devices,circuits, etc.), the terms (including any reference to a “means”) usedto describe such components are intended to correspond, unless otherwiseindicated, to any component which performs the specified function of thedescribed component (i.e., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure which performsthe function in the herein illustrated exemplary embodiments of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one of several embodiments,such feature may be combined with one or more other features of theother embodiments as may be desired and advantageous for any given orparticular application.

What is claimed is:
 1. A system for cleaning a pump/vacuum systemconnected to a low pressure chemical vapor deposition apparatus, thepump/vacuum system having a sticky TEOS material build-up therein,comprising: a supply of a composition comprising at least one loweralcohol; an injection port for introducing the composition comprising atleast one lower alcohol into the low pressure chemical vapor depositionapparatus; and the pump/vacuum system connected to the low pressurechemical vapor deposition apparatus for removing crystallized TEOSmaterial build-up, wherein the pump/vacuum system maintains a pressurefrom about 0.001 Torr to about 500 Torr during cleaning.
 2. The systemof claim 1, wherein the low pressure chemical vapor deposition apparatuscomprises a chamber and the composition comprising at least one loweralcohol is introduced into the chamber.
 3. The system of claim 1,wherein the pump/vacuum system maintains a pressure from about 0.001Torr to about 100 Torr during cleaning.
 4. The system of claim 1,wherein the composition further comprises at least one of water, a lowerorganic compound, and an inert gas.
 5. The system of claim 1, whereinthe lower alcohol comprises methanol, ethanol, n-propanol, isopropanol,n-butanol, isobutanol, t-butyl alcohol, pentanol, t-pentyl alcohol,neopentanol, hexanol, cyclohexanol, 3-methyl-2-pentanol, and mixtures oftwo or more thereof.
 6. A system for cleaning a pump/vacuum systemconnected to a low pressure chemical vapor deposition apparatus, thepump/vacuum system having a sticky TEOS material build-up therein,comprising: a supply of a gas comprising at least one lower alcohol forconverting the sticky TEOS material build-up to a crystallized TEOSmaterial build-up; an injection port for introducing the gas comprisingat least one lower alcohol into the low pressure chemical vapordeposition apparatus; and the pump/vacuum system connected to the lowpressure chemical vapor deposition apparatus for removing thecrystallized TEOS material build-up, wherein the pump/vacuumsystem,maintains a pressure from about 0.001 Torr to about 500 Torrduring cleaning.
 7. The system of claim 6, wherein the pump/vacuumsystem maintains a pressure from about 0.05 Torr to about 500 Torrduring cleaning.
 8. The system of claim 6, wherein the pump/vacuumsystem maintains a pressure from about 0.001 Torr to about 100 Torrduring cleaning.
 9. The system of claim 6, wherein the gas furthercomprises at least one of an inert gas and water vapor.
 10. The systemof claim 6, wherein the lower alcohol comprises methanol, ethanol,n-propanol, isopropanol, n-butanol, isobutanol, t-butyl alcohol,pentanol, t-pentyl alcohol, neopentanol, hexanol, cyclohexanol,3-methyl-2-pentanol, and mixtures of two or more thereof.
 11. The methodof claim 6, wherein the gas further comprises one of acetone,methylethyl ketone, methylisobutyl ketone, ethyl acetate, and mixturesthereof.
 12. The method of claim 6, wherein the gas comprises from about1% to about 100% by weight of at least one lower alcohol, from about 0%to about 99% by weight of water vapor, from about 0% to about 99% byweight of at least one lower organic compound, and from about 0% toabout 99% by weight of at least one inert gas.
 13. A system for cleaninga pump/vacuum system connected to a low pressure chemical vapordeposition apparatus, the pump/vacuum system having a sticky TEOSmaterial build-up therein, comprising: a supply of isopropyl alcohol forconverting the sticky TEOS material build-up to a crystallized TEOSmaterial build-up; an injection port for introducing the isopropylalcohol into the low pressure chemical vapor deposition apparatus; andthe pump/vacuum system connected to the low pressure chemical vapordeposition apparatus for removing the crystallized TEOS materialbuild-up, wherein the pump/vacuum system maintains a pressure from about0.001 Torr to about 500 Torr during cleaning.
 14. The method of claim13, wherein the supply of isopropyl alcohol further comprises one ofacetone, methylethyl ketone, methylisobutyl ketone, ethyl acetate, andmixtures thereof.
 15. The system of claim 13, wherein the supply ofisopropyl alcohol further comprises at least one of an inert gas andwater.
 16. The system of claim 13, wherein the pump/vacuum systemmaintains a pressure from about 0.001 Torr to about 100 Torr duringcleaning.
 17. The system of claim 13, wherein the isopropyl alcohol isin the form of a gas.